1. Field of the Invention
The present invention relates to a process and an apparatus therefor for taking a minute volume of a solution from a reservoir and injecting the solution into a vessel with high precision.
2. Description of the Prior Art
An injection apparatus for delivering minute volumes each ranging from several .mu.l to several hundred .mu.l of a sample solution is generally used in biochemical immunoassay (IA) and liquid chromatography.
Previous injection apparatuses are usually provided with a cylinder device connected to the cavity of a nozzle device into which an object solution is sucked. The solution is sucked by the backward motion of a piston of the cylinder device and injected into a vessel by the forward motion of the piston. However, when this kind of an injection apparatus is used to inject minute volumes of a solution as mentioned above, significant errors of injection have often occurred.
Provided that the lower end of the nozzle in an inverted conical shape has a diameter of about 0.3-0.5 mm and the tube wall is about 0.3-0.5 mm thick, an injection error of several .mu.l is inevitable when about 200 .mu.l of a solution is sucked and injected by the forward and backward motion of a piston in the cylinder device. The error is not negligibly small when a high injection precision is required. The error of course becomes more remarkable when a minute volume such as several .mu.l to several ten .mu.l is concerned.